practicals

Question 1

Describe the titration practical

Answer 1

1) Use a pipette to tansfer 25cmcubed of sodium hydroxide solution into a conical flask

2) add 5 drops of an indicator to the alkali in the flask

3) Use a white tile under the conical flask to see a colour change more clearly

4) Fill a burrete with sulfuric acid

5) add acid to the alkali until the solution is neutral once a colour change is seen add the acid drop by drop until the solution is neutral. It is importsnt to swirl the solution to make sure the acid and alkali mix

6)Read the volume of acid in the burette

Question 3

What to do to make the experiment more accurate

Answer 3

Mix/swirl the flask while acid is poured

repeat experiment and calculate a mean

when reading the burette, ignore bubbles

Question 4

What is the titration formula

Answer 4

sulfuric acid + sodium hydroxide -> sodium sulfate + water

Question 5

Why can’t solid ionic compounds conduct electricity

Answer 5

the ions are locked in place and are not free to move

strong electrostatic forces of attraction

Question 6

In electrolysis how do we use ionic compounds

Answer 6

It is melted or dissolved in water, this breaks the forces of attraction and the ions are free to move

These liquids can now conduct electricity

scientists call these liquids electrolytes

Question 7

cathode

Answer 7

negative electrode

Question 8

anode

Answer 8

positive electrode

Question 9

What happens at the anode and cathode

Answer 9

At the anode, the negative ions are attracted to the anode and loose electrons to become oxidised as they loose electrons

At the cathode the positive ions are attracted and gain electrons, becoming reduced

Question 10

What is produced at the cathode if the metal is more reactive than hydrogen

Answer 10

hydrogen

(copper and silver are less reactive)

Question 11

what is produced at the anode

Answer 11

oxygen

Question 12

What is used as an electrode and why

Answer 12

platnum is used as it is inert
Graphite, made out of carbon and a good conductor of electricity and a high melting point

Question 13

How do we electrolyse aluminium oxide

Answer 13

1) aluminium oxide has a high melting point so first it’s mixed with cryolite which lowers the melting point

2)Then we apply an electric current to the aluminium oxide

3) Al3+ is attracted to cathode, gains electrons and forms aluminium atom (reduction)

4) O2- are attracted to anode, (oxidised)

Question 14

Why do we use cryolite

Answer 14

reduces the amount of energy needed to melt aluminium oxide and so it saves money

Question 17

What’s wrong with electrolysis

Answer 17

The anode must be replaced regularly because the oxgygen produced at the anode react with the graphite(carbon) to form carbon dioxide gas.

a lot of energy is required to produce an electric current